Vaccines are the established and proven method to prevent diseases. As a technological platform they are also expanding into nontraditional applications such as cancer and Alzheimer's therapy, but continue to be relevant in infectious diseases research, including strategies for controlling pandemic Influenza virus. Proper selection and use of adjuvant formulations can overcome barriers to vaccine efficacy by promoting long-lasting protective immunity, overcoming poor immunity in high-risk populations (i.e., young, elderly, immunocompromised), and/or simply augmenting the existing antigen supply to reach a greater number of people (dose-sparing). The objective of this proposal is to develop next generation adjuvants based on the A-subunit of the heat-labile enterotoxin from Escherichia coli (LT), including LTA and LTA1. The enterotoxin family of adjuvants are powerful mucosal adjuvants, but have been hindered by major safety concerns in past clinical trials, particularly for intranasal delivery. Our preliminary studies indicate LTA and LTA1 proteins are safe and effective mucosal adjuvants because they can achieve broad mucosal and systemic immunity without the potential safety risks of the parent proteins and high levels of immunogenicity (i.e., anti-LT antibodies). In this proposal, we will critically evaluate LTA and LTA1 as adjuvants in combination with inactivated, pandemic influenza antigen. In our studies, we will determine how these adjuvants (1) improve correlates of protective immunity and responses to viral challenge by intranasal or intradermal influenza vaccination, (2) provide a new, safe and stable alternative to their parent protein or related B-subunit containing derivatives, (3) improve vaccination efficacy through cAMP-mediated dendritic cell activation and Th17 induction. Upon completion of this investigation, we expect to generate clear safety and efficacy data using a candidate influenza antigen for intranasal and intradermal immunization, specifically valuable for future human use in a pandemic disease setting or for use in high-risk populations. Based on the nature of the information generated by this proposal, we will also provide clear rational for novel LTA and LTA1 adjuvant inclusion in other unique vaccine formulations targeting bacterial and viral pathogens or degenerative disease like cancer.